The present invention relates to a tool or instrument with at least one wear-resistant hard coating and to a method for the production of the coating.
The known tools and instruments for working organic materials due to their field of application require a basic body with an extremely high toughness. Steels have these characteristics; however, they are not corrosion-resistant. As a protection against corrosion the known tools and instruments were chromium-plated. This chromium layer could only temporarily protect the basic body in an aggressive environment; after only a short time it peeled off.
From German patent application DE-OS 36 39 469 a further cutting and form tool with high wear-resistance and corrosion reduction is known which has several intermediate layers and a black covering coating comprising a hard carbon coating (iC) with embedded crystallites of the carbide of the intermediate layer. The first one of the intermediate layers comprises an element of group IVb or Vb of the periodic system of elements (titanium, zirconium, hafnium, vanadium, niobium or tantalum), the second layer comprises a nitride of this element, and the third layer comprises a carbide layer of the same element.
The corrosion resistance of other known cutting and form tools is specifically deficient in the processing of organic materials inter alia in their use as vulcanization and synthetic material forms for injection moulding. A separation of the layer in the salt spray mist test already occurred after 48 hours, i.e. tools and instruments coated in such a way are not safe for multiple use in dishwashing machines and for multiple sterilization. The production method in which three intermediate layers must be applied on a basic body of the cutting and form tool furthermore is elaborate. The black to anthracite-colored surface produces visually unattractive cutting tools, e.g. for household or for surgical instruments.